1. Field of the Invention
This invention relates to 1H-imidazo[4,5-c]quinoline compounds. In other aspects, this invention relates to antiviral 1H-imidazo[4,5-c]quinolin-4-amines, intermediates for the preparation of such compounds, pharmaceutical compositions containing such compounds, and pharmacological methods of using such compounds.
2. Description of the Related Art
The first reliable report of the 1H-imidazo-[4,5-c]quinoline ring system, Backman et al., J. Org. Chem. 15, 1278-1284 (1950), describes the synthesis of 1-(6-methoxy-8-quinolinyl)-2-methyl-1H-imidazo[4,5-c]quinoline for possible use as an antimalarial agent. Subsequently, syntheses of various substituted 1H-imidazo[4,5-c]quinolines have been reported. For example, Jain et al., J. Med. Chem. 11, pp. 87-92 (1968), has synthesized the compound 1-[2-(4-piperidyl)ethyl]-1H-imidazo[4,5-c]quinoline as a possible anticonvulsant and cardiovascular agent. Also, Baranov et al., Chem. Abs. 85, 94362 (1976), has reported several 2-oxoimidazo[4,5-c]quinolines, and Berenyi et al., J. Heterocyclic Chem. 18, 1537-1540 (1981), has reported certain 2-oxoimidazo[4,5-c]quinolines.
Certain antiviral 1H-imidazo[4,5-c]quinolin-4-amines are described in U.S. Pat. No. 4,689,338 (Gerster). These compounds are substituted on the 1-position by alkyl, hydroxyalkyl, acyloxyalkyl, benzyl, phenylethyl or substituted phenylethyl, and at the 2-position with hydrogen, alkyl, benzyl, or substituted benzyl, phenylethyl or phenyl. Furthermore, these compounds are known to induce interferon biosynthesis. Other antiviral 1H-imidazo[4,5-c]quinolin-4-amines, substituted on the 1-position by alkenyl substituents, are described in U.S. Pat. No. 4,929,624 (Gerster).
U.S. Pat. No. 4,698,348 (Gerster) discloses 1H-imidazo[4,5-c]quinolines that are active as bronchodilators, such as 4-substituted 1H-imidazo-[4,5-c]quinolines wherein the 4-substituent is, inter alia, hydrogen, chloro, alkylamino, or dialkylamino, and the 2-substituent is, inter alia, hydroxyalkyl, aminoalkyl, or alkanamidoalkyl. Said patent also discloses 3-amino and 3-nitro quinoline intermediates substituted at the 4-position by hydroxyalkylamino or cyclohexylmethylamino, and 1H-imidazo[4,5-c]quinoline N-oxide intermediates substituted at the 2-position with, inter alia, hydroxyalkyl, aminoalkyl, or alkanamidoalkyl.
This invention provides compounds of Formula I: 
wherein
R1 is selected from the group consisting of: hydrogen; straight chain or branched chain alkyl containing one to about ten carbon atoms and substituted straight chain or branched chain alkyl containing one to about ten carbon atoms, wherein the substituent is selected from the group consisting of cycloalkyl containing three to about six carbon atoms and cycloalkyl containing three to about six carbon atoms substituted by straight chain or branched chain alkyl containing one to about four carbon atoms; straight chain or branched chain alkenyl containing two to about ten carbon atoms and substituted straight chain or branched chain alkenyl containing two to about ten carbon atoms, wherein the substituent is selected from the group consisting of cycloalkyl containing three to about six carbon atoms and cycloalkyl containing three to about six carbon atoms substituted by straight chain or branched chain alkyl containing one to about four carbon atoms; hydroxyalkyl of one to about six carbon atoms; alkoxyalkyl wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains one to about six carbon atoms; acyloxyalkyl wherein the acyloxy moiety is alkanoyloxy of two to about four carbon atoms or benzoyloxy, and the alkyl moiety contains one to about six carbon atoms; benzyl; (phenyl)ethyl; and phenyl; said benzyl, (phenyl)ethyl, or phenyl substituent being optionally substituted on the benzene ring by one or two moieties independently selected from the group consisting of alkyl of one to about four carbon atoms, alkoxy of one to about four carbon atoms, and halogen, with the proviso that if said benzene ring is substituted by two of said moieties, then the moieties together contain no more than six carbon atoms;
R2 and R3 are independently selected from the group consisting of hydrogen, alkyl of one to about four carbon atoms, phenyl, and substituted phenyl wherein the substituent is selected from the group consisting of alkyl of one to about four carbon atoms, alkoxy of one to about four carbon atoms, and halogen;
X is selected from the group consisting of alkoxy containing one to about four carbon atoms, alkoxyalkyl wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains one to about four carbon atoms, hydroxyalkyl of one to about four carbon atoms, haloalkyl of one to about four carbon atoms, alkylamido wherein the alkyl group contains one to about four carbon atoms, amino, substituted amino wherein the substituent is alkyl or hydroxyalkyl of one to about four carbon atoms, azido, chloro, hydroxy, 1-morpholino, 1-pyrrolidino, and alkylthio of one to about four carbon atoms; and
R is selected from the group consisting of hydrogen, straight chain or branched chain alkoxy containing one to about four carbon atoms, halogen, and straight chain or branched chain alkyl containing one to about four carbon atoms;
or a pharmaceutically acceptable acid addition salt thereof.
This invention provides intermediate compounds of Formula V(a) 
wherein R is as defined above, Y is xe2x80x94NO2 or xe2x80x94NH2, and R4 is alkoxyalkyl wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains two to about six carbon atoms.
This invention provides intermediate compounds of Formula VII(a) 
wherein R is as defined above in connection with Formula V(a) and R4xe2x80x2 is alkoxy alkol wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains one to about six carbon atoms.
This invention provides intermediate compounds of Formula IX(a) 
wherein
R, R2, and R3 are as defined above;
R5 is selected from the group consisting of: straight chain or branched chain alkyl containing one to about ten carbon atoms and substituted straight chain or branched chain alkyl containing one to about ten carbon atoms, wherein the substituent is selected from the group consisting of cycloalkyl containing three to about six carbon atoms and cycloalkyl containing three to about six carbon atoms substituted by straight chain or branched chain alkyl containing one to about four carbon atoms; straight chain or branched chain alkenyl containing two to about ten carbon atoms and substituted straight chain or branched chain alkenyl containing two to about ten carbon atoms, wherein the substituent is selected from the group consisting of cycloalkyl containing three to about six carbon atoms and cycloalkyl containing three to about six carbon atoms substituted by straight chain or branched chain alkyl containing one to about four carbon atoms; alkoxyalkyl wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains one to about six carbon atoms; acyloxyalkyl wherein the acyloxy moiety is alkanoyloxy of two to about four carbon atoms or benzoyloxy, and the alkyl moiety contains one to about six carbon atoms; benzyl; (phenyl)ethyl; and phenyl; said benzyl, (phenyl)ethyl, or phenyl substituent being optionally substituted on the benzene ring by one or two moieties independently selected from the group consisting of alkyl of one to about four carbon atoms, alkoxy of one to about four carbon atoms, and halogen, with the proviso that if said benzene ring is substituted by two of said moieties, then the moieties together contain no more than six carbon atoms; and
G is selected from the group consisting of alkoxy containing one to about four carbon atoms, alkoxyalkyl wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains one to about four carbon atoms, alkylamido wherein the alkyl group contains one to about four carbon atoms, azido, chloro, 1-morpholino, 1-pyrrolidino, alkylthio of one to about four carbon atoms, alkanoyloxy, alkanoyloxyalkyl wherein the alkyl moiety contains one to about four carbon atoms, and aroyloxy, with the proviso that when G is alkylamido then R5 is alkenyl, substituted alkenyl, or alkoxyalkyl.
Further this invention provides compounds of Formula XI(a) 
wherein
R, R2, R3 and R5 are as defined above,
Z is selected from the group consisting of alkoxy containing one to about four carbon atoms, alkoxyalkyl wherein the alkoxy moiety contains one to about four carbon atoms and the alkyl moiety contains one to about four carbon atoms, hydroxyalkyl containing one to about four carbon atoms, oxoalkyl containing two to about four carbon atoms, alkanoyloxyalkyl wherein the alkyl moiety contains one to about four carbon atoms, alkylamido wherein the alkyl group contains one to about four carbon atoms, substituted amino wherein the substituent is alkyl or hydroxyalkyl of one to about four carbon atoms, azido, chloro, 1-morpholino, 1-pyrrolidino, alkylthio of one to about four carbon atoms, hydroxy, alkanoyloxy, and aroyloxy; and
Q is selected from the group consisting of hydrogen, chloro, and Rixe2x80x94Exe2x80x94NHxe2x80x94 wherein Ri is an organic group substantially inert to quinoline N-oxides and E is a hydrolytically active functional group, with the proviso that when Q is Rixe2x80x94Exe2x80x94NHxe2x80x94, then Z is other than hydroxy, substituted amino, or hydroxyalkyl, and with the further proviso that when Q is hydrogen or chloro and Z is alkylamido or hydroxyalkyl, then R5 is alkenyl, substituted alkenyl, or alkoxyalkyl.
R1 of Formula I preferably contains two to about ten carbon atoms. More preferably R1 contains two to about eight carbon atoms. Most preferably, R1 is 2-methylpropyl or benzyl.
X of Formula I is preferably azido, hydroxy, ethoxy, methoxy, 1-morpholino, or methylthio, particularly in embodiments wherein R1 is 2-methylpropyl, 2-hydroxy-2-methylpropyl, or benzyl.
Other substituents in compounds of Formula I that contain an alkyl radical (e.g., R when R is alkoxy or alkyl, or X when X is alkylamido) preferably contain two carbon atoms or, more preferably, one carbon atom in each alkyl radical.
It is preferred that R of Formula I be hydrogen.
Most preferred compounds of Formula I include 4-amino-xcex1-butyl-1-(2-methylpropyl)-1H-imidazo[4,5-c]quinoline-2-methanol hemihydrate, 4-amino-xcex1,xcex1-dimethyl-2-ethoxymethyl-1H-imidazo[4,5-c]quinoline-1-ethanol, 2-ethoxymethyl-1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine, and 4-amino-1-phenylmethyl-1H-imidazo[4,5-c]quinoline-2-methanol.
A compound of the invention can be prepared as described in the Reaction Scheme below, wherein R, R1, R2, R3, and X are as defined above and wherein P is a hydroxyl protecting group that can subsequently be removed, such as alkanoyloxy (e.g., acetoxy), or aroyloxy (e.g., benzoyloxy), and R5 is as defined for R1 above absent hydroxyalkyl and hydrogen.
Many quinolines of Formula III are known compounds (see, for example, U.S. Pat. No. 3,700,674 and references cited therein). Those that are not known can be prepared by known methods, for example, from 4-hydroxy-3-nitroquinolines as illustrated in step (1) of Scheme I. Step (1) can be conducted by reacting the 4-hydroxy-3-nitroquinoline of Formula II with a chlorinating agent such as thionyl chloride or phosphorus oxychloride. The reaction is preferably conducted in N,N-dimethylformamide, optionally in the presence of methylene chloride, and is preferably accompanied by heating. Preferably, a large molar excess of phosphorus oxychloride is avoided. Use of about 1-2 moles of phosphorus oxychloride per mole of the 4-hydroxy-3-nitroquinoline of Formula II has been found to be particularly preferable.
In step (2) a 3-nitro-4-chloroquinoline of Formula III is reacted by heating with an amine of the formula R5NH2, wherein R5 is as defined above, in a suitable solvent such as water, dichloromethane, or tetrahydrofuran, to provide a quinoline of Formula IV. Steps (1) and (2) can be combined such that the 3-nitro-4-chloroquinoline need not be isolated prior to reaction with the compound of the formula R5NH2. Such a reaction is exemplified in Example 134 and Example 188 (Step A) of U.S. Pat. No. 4,689,338, the disclosure of which is incorporated herein by reference.
A compound of Formula IV is reduced in step (3) preferably using a catalyst such as platinum on carbon, to provide a compound of Formula V. This can be carried out conveniently on a Parr apparatus in an inert solvent such as toluene or a lower alkanol.
In step (4) an intermediate compound of Formula V is reacted with (i) a carboxylic acid of the formula,
(OH)(R2)(R3)CCO2H
or (ii) a trialkyl ortho ester of the formula,
(OH)(R2)(R3)Cxe2x80x94C(OAlkyl)3
wherein xe2x80x9calkylxe2x80x9d is a straight chain or branched chain alkyl group containing one to about four carbon atoms, or (iii) a combination of such a carboxylic acid with such a trialkyl ortho ester to provide a compound of Formula VI. In any case, the reaction can be carried out by heating, e.g., at about 130xc2x0 C., in the presence of an acid, preferably a carboxylic acid of the formula
(OH)(R3)(R2)CCO2H
An alternate method of providing the 2-substituted imidazo ring is illustrated in steps (5) and (6). Step (5) involves a reaction similar to that described in connection with step (4), but involving formic acid or a trialkylorthoformate to form an intermediate of Formula VII. The intermediate of Formula VII can then be deprotonated by a strong base (e.g., an alkyllithium such as n-butyllithium) and reacted with a compound of the formula 
to form an intermediate of Formula VI.
Step (7) involves protecting the hydroxyl group with a removable protecting group such as an alkanoyloxy group (e.g., acetoxy) or an aroyloxy group (e.g., benzoyloxy). In instances wherein a hydroxyl group is present in the 1-substituent, it too can be protected in step (7) and later removed as appropriate when it will no longer interfere with subsequent reactions. Suitable protecting groups and reactions for their placement and removal are well known to those skilled in the art. See, for example, U.S. Pat. No. 4,689,338 (Gerster), Examples 115-123.
Step (8) provides an intermediate of Formula IX, through oxidation of a compound of Formula VIII with a conventional oxidizing agent that is capable of forming N-oxides. Preferred oxidizing agents include peroxyacids and hydrogen peroxide. Heating is generally employed to accelerate the rate of reaction.
In step (9) an N-oxide of Formula IX is heated in the presence of a suitable chlorinating agent such as phosphorus oxychloride to provide a chlorinated intermediate of Formula X.
In step (10) the 4-chloro group is replaced by a 4-amino group and the protecting group P is removed to provide a compound of Formula XII (a subgenus of Formula I). The amination reaction is carried out in the presence of ammonium hydroxide or, preferably, ammonia. Preferably the intermediate of Formula X is heated at 125xc2x0 to 175xc2x0 C. under pressure for 6-24 hours. Preferably the reaction is conducted in a sealed reactor in the presence of either ammonium hydroxide or a solution of ammonia in an alkanol, (e.g., preferably about 5% to about 15% ammonia in methanol).
A compound of Formula XII can also be prepared by way of step (9a) of the Reaction Scheme. Step (9a) involves (i) reacting a compound of Formula IX with an acylating agent; (ii) reacting the product with an aminating agent; and (iii) isolating the compound of Formula XII. Part (i) of step (9a) involves reacting an N-oxide with an acylating agent. Suitable acylating agents include alkyl- or arylsulfonyl chlorides (e.g., benzenesulfonyl chloride, methanesulfonyl chloride, p-toluenesulfonyl chloride). Arylsulfonyl chlorides are preferred. p-Toluenesulfonyl chloride is most preferred. Part (ii) of step (9a) involves reacting the product of part (i) with an excess of an aminating agent. Suitable aminating agents include ammonia (e.g., in the form of ammonium hydroxide) and ammonium salts (e.g., ammonium carbonate, ammonium bicarbonate, and ammonium phosphate). Ammonium hydroxide is preferred. The reaction of step (9a) is preferably carried out by dissolving the N-oxide of Formula IX in an inert solvent such as methylene chloride, adding the aminating agent to the solution, and then adding the acylating agent. Preferred conditions involve cooling to about 0xc2x0 C. to about 5xc2x0 C. during the addition of the acylating agent. Heating or cooling can be used to control the rate of the reaction. Step (9a) also involves removal of protecting group P as discussed above in connection with step (7). A further alternative method of preparing a compound of Formula XII is shown in steps (11) and (12).
Step (11) involves reacting an N-oxide with an isocyanate wherein the isocyanato group is bonded to a hydrolytically active functional group. The term xe2x80x9chydrolytically active functional groupxe2x80x9d as used herein designates any functional group that is capable of being subjected to a nucleophilic displacement reaction in step (12) of the Reaction Scheme. Exemplary hydrolytically active functional groups include carbonyl 
A particular class of such isocyanates is isocyanates of the formula Rixe2x80x94Exe2x80x94NCO, wherein Ri is an organic group substantially inert to quinoline N-oxides under the conditions of step (11) and E is a hydrolytically active functional group. Suitable Ri groups are easily selected by those skilled in the art. Preferred groups Ri include alkyl, aryl, alkenyl, and combinations thereof. Particular preferred isocyanates include aroyl isocyanates such as benzoylisocyanate. The reaction of the isocyanate with the N-oxide is carried out under substantially anhydrous conditions by adding the isocyanate to a solution of the N-oxide in an inert 
solvent such as dichloromethane. The resulting 4-substituted compound of Formula XI can be isolated by removal of the solvent.
Step (12) of the Reaction Scheme involves hydrolysis of a compound of Formula XI. The term xe2x80x9chydrolysisxe2x80x9d as used herein designates not only nucleophilic displacement with water but also displacement with other nucleophilic compounds. Such a reaction can be carried out by general methods well known to those skilled in the art, e.g., by heating in the presence of a nucleophilic solvent such as water or a lower alkanol optionally in the presence of a catalyst such as an alkali metal hydroxide or lower alkoxide.
In steps (9a), (10) or (12) a compound comprising a protecting group such as acetoxy, benzoyloxy, or the like, is deprotected to afford a compound comprising a hydroxyl group. A hydroxyl-containing compound of Formula I can be converted or elaborated by methods well known to the skilled in the art to afford a further compound of Formula I. For example, reaction with thionyl chloride will provide a compound of Formula I wherein X is chloro. Reaction of this compound with a nucleophile such as sodium azide, pyrrolidine, methanethiol, or morpholine will afford a compound of Formula I wherein X is azido, 1-pyrrolidino, thiomethyl, or 1-morpholino, respectively. Reduction of an azido compound provides a compound of Formula I wherein X is amino. Such an amino compound can be acylated to form a compound wherein X is alkylamido.
Some compounds of Formula I can be prepared by a similar reaction scheme wherein the group X is introduced directly in step (4) in which case hydroxyalkyl substituents will be tolerated at the 1-position with appropriate use of the various protection and deprotection steps.
Substituents at the 2-position can be introduced by reacting a compound of Formula XIII 
wherein R and R5 are as defined above, with a lithiating agent such a lithium diisopropylamide or n-butyllithium in a polar aprotic solvent to afford a compound lithiated on the 2-methyl group. The lithiated compound can then be reacted with an appropriate reagent containing a leaving group capable of being displaced by the lithiated 2-methyl group, such as, e.g., chloromethylmethylether or N-methoxy-N-methylacetamide, in order to elaborate the 2-methyl group. Such compounds can then be carried on as appropriate to compounds of Formula I.
A further alternate process for preparing certain compounds of Formula I involves as a first step the preparation of a 3-amino-4-(substituted)amino-2-chloroquinoline according to the method set forth in U.S. Pat. No. 4,988,815 (Andre et al., incorporated herein by reference). This compound is then reacted in a polar aprotic solvent with a carboxylic acid halide, which reacts at the 3-amino group to afford the corresponding 3-carboxamido-4-(substituted)amino-2-chloroquinoline. This compound is then reacted with ammonia, e.g., in a hydroxylic solvent such as methanol, at an elevated temperature (e.g., 100-150xc2x0 C.) to effect 1) cyclization and 2) amination at the 4-position, resulting in a 1-substituted, 2-substituted 1H-imidazo[4,5-c]quinolin-4-amine.
While not all compounds of Formula I can be prepared by the illustrated reaction scheme, known schemes can be easily adapted by those skilled in the art in order to prepare compounds other than those exemplified herein. For example, compounds wherein R1 is alkenyl can be prepared using the general schemes or adaptations thereof set forth in U.S. Pat. No. 4,929,624 (Gerster et al.) and compounds wherein R1 is hydrogen can be prepared using the general schemes or adaptations thereof set forth in commonly assigned copending application Ser. No. 07/484,761 (Gerster), both being incorporated herein by reference. A further synthetic scheme that can be used by those skilled in the art in the preparation of some of the compounds of the invention is disclosed in U.S. Pat. No. 4,988,815 (Andre"" et al.) incorporated herein by reference. Further, those skilled in the art will recognize that alteration of reaction sequence and utilization of conventional synthetic alternatives will allow the preparation of the compounds of the invention not amenable to the illustrated scheme.
The product compound of Formula I can be isolated by the conventional means disclosed in U.S. Pat. No. 4,689,338 (Gerster), such as, for example, removal of the solvent and recrystallization from an appropriate solvent (e.g., N,N-dimethylformamide) or solvent mixture, or by dissolution in an appropriate solvent (such as methanol) and re-precipitation by addition of a second solvent in which the compound is insoluble.
A compound of Formula I can be used as an antiviral agent itself or it can be used in the form of a pharmaceutically acceptable acid-addition salt such as a hydrochloride, dihydrogen sulfate, trihydrogen phosphate, hydrogen nitrate, methanesulfonate or a salt of another pharmaceutically acceptable acid. A pharmaceutically acceptable acid-addition salt of a compound of Formula I can be prepared, generally by reaction of the compound with an equimolar amount of a relatively strong acid, preferably an inorganic acid such as hydrochloric, sulfuric, or phosphoric acid, or an organic acid such as methanesulfonic acid, in a polar solvent. Isolation of the salt is facilitated by the addition of a solvent, such as diethyl ether, in which the salt is insoluble.
A compound of the invention can be formulated for the various routes of administration in a pharmaceutically acceptable vehicle, such as water or polyethylene glycol, along with suitable adjuvants, excipients, and the like. Particular formulations will be easily selected by those skilled in the art. Suitable formulations for topical application include creams, ointments and like formulations known to those skilled in the art. Formulations generally contain less than 10% by weight of a compound of Formula I, preferably about 0.1% to 5% by weight of a compound of Formula I.
The compounds of Formula I exhibit antiviral activity in mammals. They can therefore be used to control viral infections. For example, a compound of Formula I can be used as an agent to control infections in mammals caused by Type II Herpes simplex virus. Compounds of Formula I can also be used to treat a herpes infection by oral, topical, or intraperitoneal administration.
A number of compounds of Formula I were tested and found to induce biosynthesis of interferon in human cells and in mice. Furthermore, a number of compounds of Formula I were tested and found to inhibit tumors in mice. The test methods and results are set forth below. These results suggest that at least certain compounds of the invention might be useful in treating other diseases such as rheumatoid arthritis, warts, eczema, Hepatitis B, psoriasis, multiple sclerosis, essential thrombocythaemia, cancer such as basal cell carcinoma, and other neoplastic diseases.